Local muscle metabolic demand induced by neuromuscular electrical stimulation and voluntary contractions at different force levels: a NIRS study

Functional Muscle metabolic demand during contractions evoked by neuromuscular electrical stimulation (NMES) has been consistently documented to be greater than voluntary contractions (VOL) at the same force level (10-50% maximal voluntary contraction-MVC). However, we have shown using a near-infrared spectroscopy (NIRS) technique that local muscle metabolic demand is similar between NMES and VOL performed at MVC levels, thus controversy exists. This study therefore compared biceps brachii muscle metabolic demand (tissue oxygenation index-TOI and total hemoglobin volume-tHb) during a 10s isometric contraction of the elbow flexors between NMES (stimulation frequency of 30Hz and current level to evoke 30% MVC) and VOL at 30% MVC (VOL-30%MVC) and MVC (VOL-MVC) level in 8 healthy men (23-33-y). Greater changes in TOI and tHb induced by NMES than VOL-30%MVC confirm previous studies of a greater local metabolic demand for NMES than VOL at the same force level. The same TOI and tHb changes for NMES and VOL-MVC suggest that local muscle metabolic demand and intramuscular pressure were similar between conditions. In conclusion, these findings indicate that NMES induce a similar local muscle metabolic demand as that of maximal VOL

Exergaming as a viable therapeutic tool to improve static and dynamic balance among older adults and people with idiopathic Parkinson\u27s disease: a systematic review and meta-analysis

The use of virtual reality games (known as "exergaming") as a neurorehabilitation tool is gaining interest. Therefore, we aim to collate evidence for the effects of exergaming on the balance and postural control of older adults and people with idiopathic Parkinson\u27s disease (IPD). Six electronic databases were searched, from inception to April 2015, to identify relevant studies. Standardized mean differences (SMDs) and 95% confidence intervals (CI) were used to calculate effect sizes between experimental and control groups. I (2) statistics were used to determine levels of heterogeneity. 325 older adults and 56 people with IPD who were assessed across 11 -studies. The results showed that exergaming improved static balance (SMD 1.069, 95% CI 0.563-1.576), postural control (SMD 0.826, 95% CI 0.481-1.170), and dynamic balance (SMD -0.808, 95% CI -1.192 to -0.424) in healthy older adults. Two IPD studies showed an improvement in static balance (SMD 0.124, 95% CI -0.581 to 0.828) and postural control (SMD 2.576, 95% CI 1.534-3.599). Our findings suggest that exergaming might be an appropriate therapeutic tool for improving balance and postural control in older adults, but more -large-scale trials are needed to determine if the same is true for people with IPD

Effects of ON and OFF subthalamic nucleus deep brain stimulation on cortical activation during finger movements tasks: a simultaneous fNIRS and EEG study [Abstract]

Subthalamic nucleus deep brain stimulation (STN-DBS) therapy is an effective treatment for the motor symptoms of advanced Parkinson’s disease (PD). However, the underlying neurophysiological mechanisms for the motor improvement are uncertain. We utilised a simultaneous functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) neuroimaging approach to map cortical activation changes to motor performance in a PD patient “ON” and “OFF” STN-DBS. Methods The subject was a male (76y) with bilateral STN-DBS (unipolar stimulation at 160Hz and 3.3V). The experimental design consisted of an “OFF” followed by an “ON” stimulation condition. In both conditions, the subject performed a self-paced finger tapping (FT) task followed by a finger sequence (FS) task with his right hand in blocked design (30-s task, 30-s rest, repeated 5 times). During performance of the FT/FS task with the right hand, changes from rest in oxygenated (O2Hb) and deoxygenated haemoglobin concentrations were measured by an fNIRS system (Oxymon MkIII, AMS) from 15 channels covering the contralateral cortical sensorimotor network. EEG signals from 256 channels (GES-300MR, EGI) were collected synchronously with fNIRS signals. Results/Discussion Concomitant with the improved FT/FS task performance, fNIRS results showed a reduction in contralateral cortical sensorimotor network activation (i.e. smaller and less variable increase in O2Hb over the 5 FT/FS task blocks) in the “ON” than “OFF” condition. The EEG results indicated that the mean power in the Beta and Gamma bands were lower in the “ON” than “OFF” condition. However, the mean power in the Delta band, which was approximately at the FT/FS movement frequency (1-3 Hz), was higher in the “ON” than “OFF” condition. Conclusion This case study showed that STN-DBS facilitates voluntary finger movement performance by a more efficient cortical activation pattern to perform the finger movement tasks, possibly by facilitating the voluntary frequency band (Delta) and suppressing the involuntary frequency bands (Beta/Gamma)

Less effort, better results: how does music act on prefrontal cortex in older adults during verbal encoding? An fNIRS study

Several neuroimaging studies of cognitive aging revealed deficits in episodic memory abilities as a result of prefrontal cortex (PFC) limitations. Improving episodic memory performance despite PFC deficits is thus a critical issue in aging research. Listening to music stimulates cognitive performance in several non-purely musical activities (e.g., language and memory). Thus, music could represent a rich and helpful source during verbal encoding and therefore help subsequent retrieval. Furthermore, such benefit could be reflected in less demand of PFC, which is known to be crucial for encoding processes. This study aimed to investigate whether music may improve episodic memory in older adults while decreasing the PFC activity. Sixteen healthy older adults (μ = 64.5 years) encoded lists of words presented with or without a musical background while their dorsolateral prefrontal cortex (DLPFC) activity was monitored using a eight-channel continuous-wave near-infrared spectroscopy (NIRS) system (Oxymon Mk III, Artinis, The Netherlands). Behavioral results indicated a better source-memory performance for words encoded with music compared to words encoded with silence (p < 0.05). Functional NIRS data revealed bilateral decrease of oxyhemoglobin values in the music encoding condition compared to the silence condition (p < 0.05), suggesting that music modulates the activity of the DLPFC during encoding in a less-demanding direction. Taken together, our results indicate that music can help older adults in memory performances by decreasing their PFC activity. These findings open new perspectives about music as tool for episodic memory rehabilitation on special populations with memory deficits due to frontal lobe damage such as Alzheimer\u27s patients

Complex network analysis of resting-state fMRI of the brain

Due to the fact that the brain activity hardly ever diminishes in healthy individuals, analysis of resting state functionality of the brain seems pertinent. Various resting state networks are active inside the idle brain at any time. Based on various neuro-imaging studies, it is understood that various structurally distant regions of the brain could be functionally connected. Regions of the brain, that are functionally connected, during rest constitutes to the resting state network. In the present study, we employed the complex network measures to estimate the presence of community structures within a network. Such estimate is named as modularity. Instead of using a traditional correlation matrix, we used a coherence matrix taken from the causality measure between different nodes. Our results show that in prolonged resting state the modularity starts to decrease. This decrease was observed in all the resting state networks and on both sides of the brain. Our study highlights the usage of coherence matrix instead of correlation matrix for complex network analysis

Effects of muscle contractions on biceps brachii oxygenation investigated by near-infrared spectroscopy

Oxidative metabolism is the dominant source of energy for skeletal muscle. To investigate muscle oxidative metabolism, it is necessary to measure muscle oxygen (O2) consumption during exercise. Near-infrared spectroscopy (NIRS) allows for the noninvasive investigation of muscle oxidative metabolism during exercise at a high time resolution. However, limited studies have used NIRS to compare oxidative metabolic responses of the biceps brachii during lengthening (eccentric), shortening (concentric) and static (isometric) voluntary contractions, and electrically evoked isometric contractions. Therefore, the overall purpose of this thesis was to investigate the effects of muscle contractions on biceps brachii oxygenation and haemodynamics using NIRS..

The effects of a repeated bout of eccentric exercise on indices of muscle damage and delayed onset muscle soreness

This study examined markers of muscle damage following a repeated bout of maximal isokinetic eccentric exercise performed prior to full recovery from a previous bout. Twenty non-resistance trained volunteers were randomly assigned to a control (CON, n=10) or experimental (EXP, n=10) group. Both groups performed 36 maximal isokinetic eccentric contractions of the elbow flexors of the non-dominant arm (ECC1). The EXP group repeated the same eccentric exercise bout two days later (ECC2). Total work and peak eccentric torque were recorded during each set of ECC1 and ECC2. Isometric torque, delayed onset muscle soreness (DOMS), flexed elbow angle and plasma creatine kinase (CK) activity were measured prior to and immediately following ECC1 and ECC2, at 24h intervals for 7 days following ECC1 and finally on day 11. In both groups, all dependent variables changed significantly during the 2 days following ECC1. A further acute post-exercise impairment in isometric torque (30±5%) and flexed elbow angle (20±4%) was observed following ECC2 (

Effects of transcranial direct current stimulation of the motor cortex on prefrontal cortex activation during a neuromuscular fatigue task: An fNIRS study

This study investigated whether manipulation of motor cortex excitability by transcranial direct current stimulation (tDCS) modulates neuromuscular fatigue and functional near-infrared spectroscopy (fNIRS)-derived prefrontal cortex (PFC) activation. Fifteen healthy men (27.7 ± 8.4 years) underwent anodal (2 mA, 10 min) and sham (2 mA, first 30 s only) tDCS delivered to the scalp over the right motor cortex. Subjects initially performed a baseline sustained submaximal (30 % maximal voluntary isometric contraction, MVC) isometric contraction task (SSIT) of the left elbow flexors until task failure, which was followed 50 min later by either an anodal or sham treatment condition, then a subsequent posttreatment SSIT. Endurance time (ET), torque integral (TI), and fNIRS-derived contralateral PFC oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentration changes were determined at task failure. Results indicated that during the baseline and posttreatment SSIT, there were no significant differences in TI and ET, and increases in fNIRS-derived PFC activation at task failure were observed similarly regardless of the tDCS conditions. This suggests that the PFC neuronal activation to maintain muscle force production was not modulated by anodal tDCS